What happens, though, when there are too many casualties for emergency workers to handle? When an earthquake struck Haiti last year, caregivers from around the world responded, finding thousands of people in need of medicine, water, food, and shelter. But there were not enough supplies to treat everyone.

In situations with a lack of resources, how do caregivers decide who they can save–and who’s beyond help?

Tom Kirsch, Associate Professor of Emergency Medicine at Johns Hopkins, was in Haiti in the week following the earthquake. He had to make those sorts of decisions, and he found it took a real toll on him and his colleagues. He and his wife, Margaret Moon, also a doctor at Hopkins, and a scholar in clinical ethics at the Berman Institute, wrote about the experience in an article called “The Line,” published in the Journal of the American Medical Association last spring.